Men die at higher rates than women from almost every kind of cancer, a new study finds.
Although it’s been known for years that men die of cancer more often overall, the new study is among the first to study sex differences by individual cancer site, and to analyze whether sex differences in mortality can be explained mostly by differences in cancer incidence (that is, how often men and women develop cancer) or by differences in prognosis (that is, whether men or women are more likely to survive once they’re diagnosed).
The study, which was published Tuesday in the journal Cancer Epidemiology, Biomarkers and Prevention, used data collected from 1977 to 2006 by cancer registries across the U.S. The study did not analyze data on sex-specific cancers such as testicular cancer, prostate cancer or breast cancers.
Between 1977 and 2006, the top five biggest disparities in age-adjusted cancer death rates were for the following types of cancer, according to the study:
- Cancer of the lip: 5.51 men died for every one woman
- Cancer of the larynx: 5.37 men died for every one woman
- Cancer of the hypopharynx: 4.47 men died for every one woman
- Cancer of the esophagus: 4.08 men died for every one woman
- Cancer of the bladder: 3.36 men died for every one woman
All of those cancers are relatively rare. But men also die at much higher rates from the most common forms of cancers that affect both sexes. Over the course of the study period, 2.31 men died of lung cancer for every one woman who died of lung cancer, for example, and 1.42 men died of colorectal cancer of every woman who did.
In fact, of the 36 cancer types reviewed, women had higher death rates from only three: peritoneum, omentum and mesentery cancers; gall bladder cancer; and cancer of the anus, anal canal and anorectum. All three forms are extremely rare.
The new study suggests that while some small fraction of the mortality disparity can be explained by survival differences after diagnosis, almost all of the disparity arises from the fact that men are more likely than women to develop cancers in the first place.
The study’s lead author, Michael Cook, told WebMD that the causes of men’s higher cancer incidence are “not clear cut.”
He added, however, that because the ratios of male cancer deaths to female cancer deaths were changing over time, this might implicate sex differences in carcinogenic exposures that also change over time.
Chief among them are cigarette smoking — U.S. men historically have smoked much more than women, although the numbers have evened out in the last few decades — and viral infections such as human papillomavirus (HPV). HPV is known to cause cervical cancer (which was not considered in the present study about sex disparities, as men do not have a cervix and therefore cannot develop cervical cancer). But HPV is also implicated in tongue and oropharyngeal cancer, as well as cancer of the anus, anal canal and anorectum (cancers that were considered in the present study).
Lifestyle, therefore, may well explain part of the difference. Of the five cancers with the biggest sex disparities in mortality — lip, larynx, hypopharynx, esophagus and bladder – all five have been linked to smoking, drinking or both.
The authors of the new study also say there could also be some universal mechanisms, not related to lifestyle, that might make men more susceptible to cancers. These include the different hormone profiles of men and women, as well chromosomal abnormalities, and possible differences by sex in antioxidative capacity (the body’s ability to limit damage from free radicals) or immune function.